- Make local-only function and variables static.
- Move function prototypes and extern variable declarations to
header files.
- Delete unused variables.
There's still a handful of extern declaraions that should be fixed up.
* Do rcons output properly, using cn_tab->cn_dev which points
at rcons cdevsw entrypoints.
* The pmadx console code was using keyboard (serial) device
(major,minor) for raster consoles with special code in the keyboard
drivers to catch output intended for consoles, pull it off the device
queue, and print them via cnputc().
Ifdef out RCONS_BRAINDAMAGE.
* Other minor cleanup to pmax scc driver.
